Proximity Based Selection of an Implantable Medical Device for Far Field Communication

ABSTRACT

Devices and systems provide for proximity based selection of an implantable medical device for far field communication with an external device. By using a proximity communication that is limited to the IMD of interest during the selection process, the external device can eliminate those IMDs that are in range of far field communications but are able to receive the proximity communication. Thus, information may be shared via a proximity communication that is validated via a far field communication, or shared via a far field communication as a challenge and then validated via a proximity communication. The proximity communication may be used to initially limit the number of devices that respond to a discovery request and then subsequently used to select the intended implantable medical device as well as automatically select the appropriate therapy application corresponding to the selected IMD.

TECHNICAL FIELD

Embodiments relate to far field communications between external devicesand implantable medical devices. More particularly, embodiments relateto the selection of an implantable medical device for far fieldcommunication with an external device on the basis of proximity.

BACKGROUND

Conventionally, external devices such as clinician and patientprogrammers communicate with an implantable medical device (IMD) througha near field form of communication such as an inductive coupling. Due tothe short range of the inductive coupling, a telemetry head is placed inclose proximity to the IMD to establish the inductive link. Because thetelemetry head has a very short range and consequently is in such closeproximity to the IMD, there is essentially no risk of inadvertentlycommunicating with a different nearby IMD.

Far field communication has become an alternative to the use of nearfield links between external devices and implantable medical devices.Far field communication uses frequencies that allow for electromagneticsignal propagation over significantly larger distances than the maximumdistance of near field links. This increased range of signals allows anexternal device to communicate with the IMD without placing a telemetryhead in close proximity to the IMD. However, the increased range of thefar field communication creates issues that are not a concern for nearfield links.

In particular, far field communication by the external device createsthe possibility that other IMDs besides the intended IMD are incommunication range of the external device. Therefore, the externaldevice must either have advance knowledge of an identifier of thedesired IMD or the external device must receive a user selection from alist of IMDs that respond to a discovery signal by the external device.Requiring the user to select the proper IMD from a list adds extra timeand burden to the process and also presents an opportunity for humanerror where the user may select the wrong device and/or application foran intended device.

SUMMARY

Embodiments address issues such as these and others by providingdevices, systems, and methods that utilize physical proximity of anexternal component relative to an intended IMD to allow the externaldevice to select the intended IMD for a far field communication sessionand ultimately eliminate pairing between external devices and unintendedIMDs within range of far field communications. One or more various formsof proximity communication occur between the external device and the IMDduring the establishment of the far field communication session. Thevarious forms of proximity communication occur within a short distancefrom the IMD so that the proximity communication intentionally does notextend to any unintended IMDs that may be nearby. In some cases, thephysical proximity may be removed once the far field communication hasbeen appropriately confirmed through the proximity communication. Thepairing of the intended IMD with the external device may in some casesthen allow for additional benefits such as the ability of the externaldevice to automatically run the correct application for the intendedIMD.

A form of proximity communication may share unique information betweenthe external device and the IMD that can then be verified using a farfield communication. This allows the external device to confirm that theIMD is the intended one while unintended IMDs do not have access to theunique information and cannot verify the unique information through farfield communication with the external device which allows the externaldevice to filter out discovery responses from the unintended IMDs. Aform of proximity communication may trigger the IMD to respond to a farfield discovery request by the external device while unintended IMDsthat do not receive a proximity communication at that time would notrespond to the far field discovery request. A form of proximitycommunication may be used by one device to satisfy a challenge issuedover a far field communication by the other device to confirm that thefar field communication is between the devices that are in physicalproximity to one another.

DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a typical operating environment for embodiments where anexternal device and an IMD utilize proximity communication to establisha far field communication session.

FIG. 2 shows components for one example of an external deviceembodiment.

FIG. 3 shows components for one example of an IMD embodiment.

FIG. 4 shows a first example of a procedure to establish a far fieldcommunication session where a unique value and/or key are shared via aproximity communication.

FIG. 5 shows a second example of a procedure to establish a far fieldcommunication session where a challenge is issued by the IMD during adiscovery phase.

FIG. 6 shows a third example of a procedure to establish a far fieldcommunication session where the external device requests a challengeupon the far field communication session being established.

FIG. 7 shows a fourth example of a procedure to establish a far fieldcommunication session where the IMD issues a challenge upon the farfield communication session being established.

FIG. 8 shows a fifth example of a procedure to establish a far fieldcommunication session where an encryption key is exchanged through aproximity communication.

FIG. 9 shows a sixth example of a procedure to establish a far fieldcommunication session where the external device considers far fieldsignal strength when selecting the IMD for the far field communicationsession.

DETAILED DESCRIPTION

Embodiments provide for devices, systems, and methods that allow anexternal device to select an IMD for far field communication by using aproximity communication that is limited to the IMD of interest. In doingso, the external can eliminate those IMDs that are in range of far fieldcommunications but are not privy to the proximity communication.

FIG. 1 shows an environment that includes an external device 102, suchas a clinician programmer, patient programmer, or a remote/homemonitoring device that is nearby a patient 108 who has an IMD 104. TheIMD 104 may be implanted within or mounted externally to the body 108and may perform one or more medical tasks such as cardiac orneurological stimulation, physiological sensing, drug infusion, and thelike. The IMD 104 may include components 106 such as stimulation orsensing leads or drug delivery catheters that extend from the IMD 104and terminate at the target area of the body 108.

The external device 102 ultimately communicates with the IMD 108 througha far field communication session utilizing far field signals 114 sentby the external device 102 and far field signals 116 sent by the IMD108. These far field signals 114, 116 may be radio frequency (RF)signals such as those of the Medical Implant Communications Service(MICS) band, the Industrial, Scientific, and Medical (ISM) band, or theshort range device (SRD) band. The far field communication session maybe used to program a medical therapy to the IMD, to obtain informationfrom the IMD regarding therapy and patient information, and the like.

While the single IMD 104 is shown in FIG. 1, it will be appreciated thatthere may be other IMDs and/or other external devices nearby and inrange of the far field signals 114 of the external device 102. Theexternal device 102 may not be aware of identification information ofthe intended IMD 104 in advance such that the external device 102 cannotimmediately discern far field communications of the intended IMD 104relative to far field communications of other IMDs. However, physicalproximity can be established to allow proximity communication to occurbetween the external device 102 and the intended IMD 104. Therefore, aprocedure is provided that utilizes this physical proximity at theinitiation of the far field communication session to avoid the externaldevice 102 conducting a far field communication session with anunintended nearby IMD. To allow the external device 102 to select theintended IMD 104 for far field communication and avoid selecting anunintended nearby IMD, proximity communication signals 112 may beexchanged between a proximity communicator 110 and the IMD 104 duringthe establishment of the far field communication session.

The proximity communicator 110 may be of various forms and may be aseparate component of the external device 102 or be integrated with theexternal device 102, or a combination of both. For instance, theproximity communicator 110 may be a near field telemetry head that istethered to the external device 102 by a communication path 118 such asa cable or wireless connection and that establishes an inductive linkwith the IMD 104. As another example, the proximity communicator 110 maybe an audible tone generator where the IMD 104 receives and recognizesdifferent audible tones. As another example, the proximity communicator110 may be a body thump device, such as a chest thump device, where theIMD 104 detects the thump through an on-board accelerometer or othervibration detector. As yet another example, the proximity communicator110 may be a static field generating device such as an electromagnet ora permanent magnet being moved into and out of proximity with the IMD104 by the clinician.

In some cases including the near field telemetry head, the audiblesignal generator, the body thump device, and the electromagnet, theproximity communicator 110 may be under control of the external device102 through a tethered or wireless connection between the telemetry head110 and the external device 102. In some cases including the clinicianproviding the body thump or moving the permanent magnet, the proximitycommunicator 110 is under direct control of the clinician who may befollowing commands being issued by the external device 102 to provide orremove the proximity communication.

The proximity communication may range from being a simple present orabsent signal to a more complex signal carrying data. Furthermore, theproximity communication may be a unidirectional communication mode insome embodiments, particularly where the communication is simple. Thismay reduce the cost and complexity of a device, particularly the IMD104. The proximity communication may be a bi-directional communicationmode in other embodiments, such as where one device may send datathrough a proximity communication while the other device may send anacknowledgement through a subsequent proximity communication. This mayimprove the efficiency of the proximity communication procedure.

FIG. 2 shows components of one example of the external device 102. Theexternal device 102 includes a processor 202, a memory 204, and astorage device 206. The external device 102 may also include localinput/output (I/O) ports 208 such as to provide local screen displaysand to receive user input via keyboard, mouse, and so forth. Theexternal device 102 also includes far field communication circuitry 210used to establish the far field communication session with the IMD 104.The far field communication circuitry 210 may drive a signal propagationtool such as an RF antenna. The signal propagation tool may be includedwithin the proximity communicator 110 so that the far fieldcommunication circuitry 210 instructs the signal propagation tool overthe connection 118 or the signal propagation tool may be a separateexternal component or housed within the external device 102.

In addition to the far field communication circuitry 210, the externaldevice 102 also includes proximity communication circuitry 212. Theproximity communication circuitry 212 may be of various forms tointeract with the proximity communicator 110. The link between theproximity communication circuitry 212 and the proximity communicator 110may be a wired or wireless connection, for example using universalserial bus protocol, Bluetooth® protocol, or other such protocols, thatprovides data commands to circuitry within the proximity communicator110 to produce the proximity communication signal. The proximitycommunicator 110 may then include a near field inductive driver circuit,a signal generator for producing audible tones, a motion signalgenerator for driving a body thump device, a field producing circuit fordriving an electromagnet, and the like that are responsive to the datacommands. Alternatively for a wired connection, these circuits may beincluded in the proximity communication circuitry 212 to drive theproximity communicator 110 directly.

The external device 102 may include additional communicationcapabilities that may be provided by far field communication circuitry210 or by additional communication circuitry. For instance, the externaldevice 102 may include Wi-Fi connectivity, public switched telephonenetwork connectivity, and so forth to allow for remote communication,particularly where the external device 102 is a home/remote monitor.

The memory 204 may be used to store information in use by the processor202. For instance, the memory 204 may store therapy parameters that areinput by a clinician or patient that are to be loaded into the IMD 104.The memory 204 may also store programming that is used by the processor202 to control the IMD selection procedure of the external device 102.The memory 204 may be of various types, such as volatile, non-volatile,or a combination of the two.

The storage device 206 may be used to store information for a long termand may be of various types such as non-volatile so that the informationis retained when the external device 102 is powered off. The storagedevice 206 may also store programming for the processor 202 that isimplemented to control the IMD selection procedure. Examples of thestorage device 206 include electronic, magnetic, and optical drives. Thestorage device 206 and the memory 204 are both examples of computerreadable media that may store information in the form of computerprogramming, data structures, and the like.

The processor 202 performs logical operations to provide a sequence offar field and proximity communications and related decisions such asthose of FIGS. 4-9 to allow far field communication sessions with theIMD 104 to be established. The processor 202 may be of various forms.For instance, the processor 202 may be a general-purpose programmableprocessor that executes software that is stored on the storage device206 or elsewhere. Other examples include a dedicated purpose hardwarecircuit or hard-wired digital logic. The processor 202 may be multipleseparate components or processors, dedicated hardware/state machine, andthe like. The processor 202 may communicate with the various othercomponents through one or more data buses.

FIG. 3 shows components of one example of the IMD 104. The IMD 104includes a processor 302 and a memory 304. The IMD 104 also includesmedical circuitry 306 that performs a medical task such as stimulation,drug delivery, monitoring, and the like. The IMD 104 also includes farfield communication circuitry 308 used to establish the far fieldcommunication session with the external device 102. The far fieldcommunication circuitry 308 may drive a signal propagation tool such asan integral RF antenna.

In addition to the far field communication circuitry 308, the IMD 104also includes proximity communication circuitry 310. The proximitycommunication circuitry 310 may be of various forms where for a givensystem, the type of proximity communication circuitry 310 matches thetype of proximity communicator 110 that the external device 102includes. Accordingly, the proximity communication circuitry 310 may bea near field inductive receiver, a microphone for receiving audibletones, an accelerometer or other vibration detection device, a fieldoperable switch such as a magnetic reed switch, and the like.

The memory 304 may be used to store information in use by the processor302 such as programming and data values. The memory 304 may storeadditional information including therapy parameters that are used tocontrol the medical circuitry 306. The memory 304 may be of varioustypes such as volatile, non-volatile, or a combination of the two. Thememory 304 is also an example of computer readable media that may storeinformation in the form of computer programming, data structures, andthe like.

The processor 302 performs logical operations to provide a sequence offar field and proximity communications and related decisions such asthose of FIGS. 4-9 to allow far field communication sessions with theexternal device 102 to be established. The processor 302 may be ofvarious forms like those discussed above for the processor 202 of theexternal device 102 and as discussed above may be multiple separatecomponents or processors, dedicated hardware/state machine, and thelike. The processor 302 may communicate with the various othercomponents through one or more data buses.

FIGS. 4-9 describe proximity based communications. While these examplesshow proximity communications being directed from an external device 102to an IMD 104, it will be appreciated that in some cases the roles maybe reversed and the direction of the proximity communications may bereversed whereby the IMD 104 may send proximity communications ratherthan or in addition to the external device 102 doing so.

FIG. 4 shows a first example of a procedure to establish a far fieldcommunication session where a unique value and/or key are shared via aproximity communication. The proximity communication is of a type thatcan carry data. Furthermore, the proximity communication may bebi-directional so that an acknowledgement may be returned as aconfirmation of receipt of the data so that a successful initial datatransfer via the proximity communication can be completed as aprerequisite to attempting subsequent steps.

Initially, the external device 102 may send a proximity communication104 that includes a value that is unique to the external device 102 tothe IMD 104. For example, the unique value may be a device serialnumber, hardware identification number, randomly generated number, asecurity key value, a combination, or other such values that may beunique to the external device 102. Because this information istransferred through the proximity communication 402, no other nearby IMDwill receive this information. The external device 102 also sends a farfield discovery communication 404 shortly before, during, or shortlyafter sending the proximity communication 402. The IMD 104 as well asother nearby IMDs may receive and respond to this far field discoverycommunication 404.

In one example, the IMD 102 may respond only to a discovery request thatis within a certain time of receiving the proximity communication 402,such as a simultaneous occurrence of the proximity communication 402 andthe discovery communication 404 or within a predefined delay from one tothe next. In this example, the IMD 104 and potentially other nearby IMDsas well are configured to respond by sending the unique value that eachhas received via a proximity communication and also by sending a valuethat is unique to the IMD. For example, this value may be a deviceserial number, hardware identification number, randomly generatednumber, a security key value, a combination, or other such values thatmay be unique to the IMD 104.

Only the far field response communication 406 from the IMD 104 ofinterest will have the unique value that corresponds to the externaldevice 102. Other IMDs would either have no unique value of an externaldevice to send or would send the unique value of a different externaldevice. Furthermore, in some examples, only those IMDs that receive thediscovery communication 404 within a specified time relative to aproximity communication, such as the proximity communication 402received by the intended IMD 104, bother to respond with a far fieldresponse communication such as the far field response communication 406from the intended IMD 104.

For each far field response communication, the external device 102attempts to verify the shared unique value by determining whether theunique value being received matches the unique value that was previouslysent over the proximity communication 402 at a query operation 408. If aparticular response does not include a matching value, then thatparticular response is ignored at operation 410. For the response 406which does have the matching unique value from the proximitycommunication 402, the external device 102 then associates the valuethat is unique to the IMD 104 and that is included in the far fieldresponse communication 406 to the far field communication session beingestablished at an association operation 412. The external device 102 mayalso then execute the appropriate therapy program automatically based onthe value that is unique to the IMD 104 where the external device 102stores associations of such values to therapy applications.

The external device 102 then begins the session with the IMD 104. Theexternal device may communicate during the session by using the uniquevalue of the external device 102 of which the IMD 104 is aware toidentify the sender of transmissions and/or using the unique value ofthe IMD 104 to identify the intended recipient of transmissions.Likewise, the IMD may communicate during the session by using the uniquevalue of the IMD 104 of which the external device 102 is aware toidentify the sender of transmissions and/or using the unique value ofthe external device 102 to identify the intended recipient oftransmissions.

The session may be made secure by encrypting the information with anencryption key. This encryption key may have been generated for thesession by the external device 102 and included in the proximitycommunication 402 so that the IMD 104 already has the key.Alternatively, the key may be exchanged in another manner and/or atanother time in the sequence such as by using a low power radiofrequency communication to minimize the range. Furthermore, the IMD 104may provide the key for the secure session rather than receiving the keyfrom the external device 102.

In some cases, such as for an external device 102 that is a patientprogrammer or home monitoring device, the external device 102 and theIMD 104 may be bonded whereby each device is aware of an identificationvalue of the other that is used to address far field communications andalready possesses the encryption key used to secure the far fieldcommunications. In that case, the proximity based initiation of the farfield communication session by a process like that of FIG. 4, as well asFIGS. 5-9 discussed below, may still be useful for various reasons. Forinstance, the initial proximity communication such as the proximitycommunication 402 may be used as a wake up signal for the far fieldcommunication circuits of the IMD 104. Additionally, to ensure that theuse of the external device 102 to initiate the communication session islegitimate, as opposed to being an accident or a malicious attempt,proximity must be established before the far field communication sessioncan begin. However, in such a case, the far field communication sessioncan begin pursuant to the processes of FIGS. 4-9 but with omission ofthe discovery operations because the identification of the IMD 104 isknown to the external device 102 so that it can immediately address aninitial far field communication to the IMD 104.

For embodiments using processes such as those of FIGS. 4-9 wherediscovery via far field communications is attempted, the external device102 and IMDs may be configured to apply collision avoidance and backoffalgorithms. These algorithms allow devices to re-attempt to send and/orreceive expected far field communications where two devices may attemptto send a far field communication at the same time such that neithertransmission is received and acknowledged. A re-attempt to send the farfield communication occurs by each of the sending devices but atdifferent times on the second attempts because the backoff algorithm ofeach sending device randomly chooses the time for the re-attempt. Thisreduces the likelihood of collisions occurring multiple times.

FIG. 5 shows a second example of a procedure to establish a far fieldcommunication session. In this particular example and as furtherdiscussed below, a challenge may be issued by the IMD during a discoveryphase to provide confirmation that the correct IMD has been selected.Other examples of providing confirmation or otherwise selecting theappropriate IMD are discussed with reference to FIGS. 6-9.

Initially, the external device 102 provides a proximity communication502 in the form of a signal. As discussed above, the proximitycommunication 502 may be provided by a third party such as the clinicianacting at the request of the external device 102 such as to pass amagnet nearby the IMD 104 to provide a form of the proximitycommunication 502. In either case, this signal may be simple in terms ofcarrying no data but merely being on or off. Alternatively, this signalof the proximity communication 502 from the external device 102 may bemore sophisticated including the ability to carry data such ascommunication identifiers, encryption key data, challenge data, and soforth. In either case, the IMD 104 may or may not have the ability tosend a return proximity communication.

The proximity communication of these embodiments of FIGS. 4-9, such asthe proximity communication 502 from the external device 102 may serveone or more purposes. For instance, the proximity communication 502 mayserve as a trigger for the IMD 104 to respond to far fieldcommunication. Likewise, the proximity communication 502 may serve as awake-up signal to the far field communication abilities of the IMD 104.This may be useful where the IMD 104 deactivates the far fieldcommunication abilities during periods of non-use and reactivates thoseabilities upon receiving a proximity communication 502. The opposite mayalso be true, where the IMD 104 uses the far field communicationabilities to monitor for a far field wake up signal that then wakes upthe proximity communication abilities of the IMD 104. In that case, theexternal device 102 may send a far field communication in advance ofproviding the proximity communication.

The external device 102 also sends a far field discovery communication504. This far field discovery communication 504 may occur at some pointshortly after the proximity communication 502, particularly in exampleswhere the proximity communication 502 serves as a wake-up signal to thefar field communication abilities of the IMD 104. The far fielddiscovery communication 504 may occur shortly before or during theproximity communication 502, particularly in examples where the farfield communication abilities of the IMD 104 are already functioningprior to the proximity communication 502.

The far field discovery communication 504 serves as an inquiry to allIMDs within range and triggers the receiving IMDs to provide a responsethat identifies the IMD such as by including a value unique to the IMD104 in the response to the discovery. In one example, the far fielddiscovery communication 504 specifies a condition for responding. Thecondition may be that the IMD responds only if the IMD is receiving thefar field discovery communication 504 within a predefined time relativeto receiving the proximity communication. In one example, the predefinedtime may be zero, such that the IMD must receive the proximitycommunication 502 at the time the far field discovery communication 504is received in order to provide a response.

This condition may be specified by setting a bit value within thediscovery request, where the predefined time is preconfigured within thelogic of the IMD 104. This condition may alternatively be specified in amore complex manner such as by indicating the predefined amount of timewithin the request.

In another example, the criteria for responding are preconfigured withinthe IMD 104. So, in this case, the far field discovery communication 504may omit any conditions, and the external device 102 may rely on theIMDs that receive the far field discovery communication 504 to properlydetermine whether to respond based upon the preconfiguration.

In this example, the IMD 104 detects whether the far field discoverycommunication has arrived within the predefined amount of time relativeto receiving the proximity communication 502 at a query operation 506.For those IMDs where no proximity communication 502 has been received orhas been received such that the far field discovery communication 504 isoutside of the allowed window of time, the far field discoverycommunication 504 is ignored at an operation 508. For the intended IMD104, the proximity communication 502 is received and the far fielddiscovery communication arrives within the predefined time relative tothe proximity communication 502 so that a far field responsecommunication 510 is returned.

The far field response communication 510 may specify the value that isunique to the IMD 104. The external device 102 may then utilize thisunique value to establish a communication session with the IMD 104.However, there is the possibility that multiple IMDs provide a response,including the intended IMD 104 as well as the other nearby IMDs who mayhave also had a proximity signal from other external devices present atthe appropriate time relative to the far field discovery communication504 from the external device 102. In that case, the external device 102may not determine which IMD 104 is the correct one from the far fieldresponses alone. The external device 102 may instead rely on a challengeprocedure in order to ultimately confirm that the intended IMD 104 isthe one that the external device 102 is communicating with via far fieldcommunications.

In this example, the challenge procedure may be provided by each IMDthat is responding including a challenge within the far field responsecommunication 510. The challenge may specify that the external device102 provide a proximity communication that includes a challengeresponse. The challenge response may be of various types and may dependupon the type of proximity communication that is in use. For instance,where the proximity communication is a simple on or off state of asignal, the challenge may be to provide an on-off sequence, or to be onat only a certain time or for only a certain duration. As anotherexample, where the proximity communication is capable of providing data,the challenge may be to repeat a particular data value or sequence.

In this example, the external device 102 may respond to receivingseveral responses by choosing one of the responses and attempting tosatisfy the challenge. The choice may be based on time the response wasreceived, strength of the response signal, a random selection, and thelike. When choosing whether to respond to any one of the receivedresponses, the external device 102 may detect whether each response istimely at a query operation 512 and ignore the response at an operation514 if not.

The external device 102 may proceed to setup the communication sessionalong with responding to the challenge for the chosen response.Initially, for the chosen response, the external device 102 may proceedto associate the unique value of the IMD received in the response to thesession at an association operation 516. The external device 102 mayalso then execute the appropriate therapy program automatically based onthe value that is unique to the IMD where the external device 102 storesassociations of such values to therapy applications.

The external device 102 then determines that the challenge response isnecessary at a query operation 518. A proximity communication 520 thatprovides the response to the challenge is sent if requested, and thenthe external device 102 attempts to begin a communication session withthe selected IMD via an exchange of far field communications 528. Inembodiments where no challenge was requested, such as where the externaldevice 102 is using some other technique for selecting the correct IMDthat has responded, then the external device may proceed with the farfield communications 528 without sending the challenge response 520.

The IMD 104, upon sending the far field response communication 510 maythen detect that a challenge has been sent at a query operation 522. Forembodiments where no challenge is performed such as where the externaldevice 102 uses some other technique for selecting the correct IMD 104that has responded, then the IMD 104 may proceed with the far fieldcommunications 528 to establish the communication session whereby theIMD 104 responds to far field communications that include the uniquevalue of the IMD 104 as the recipient.

For embodiments where the IMD 104 has issued the challenge to theexternal device 102, the IMD 104 may then detect whether the sharedchallenge is verified by detecting whether the challenge response hasbeen received and whether the challenge response matches the challengethat was issued at a query operation 524. Because the IMD 104 isreceiving proximity communications from the external device 102, the IMD104 will receive the proximity communication 520 that includes thechallenge response regardless of whether the external device 102 isresponding to the challenge by the IMD 104 or a challenge by anothernearby IMD. However, if the external device 102 is responding to achallenge by another nearby IMD, then because the challenge from eachIMD is different the challenge response being provided to the IMD 104will not match the challenge that was issued by the IMD 104.Accordingly, the IMD 104 will ignore all subsequent communication at anoperation 526 because the external device 102 has selected anothernearby and unintended IMD rather than the intended IMD 104. The IMD 104may continue to ignore subsequent communication until the discoveryprocess of FIG. 5 re-starts with another proximity communication 502 andfar field discovery communication 504.

The other nearby IMD that has been incorrectly selected by the externaldevice 102 will not receive the proximity communication 520 from theexternal device 102 that includes the challenge response because theother nearby IMD is not within range of the proximity communication 520.If this other IMD does not receive a challenge response, then this othernearby IMD also ignores all subsequent communication until the discoveryprocess of FIG. 5 re-starts with another proximity communication 502 andfar field discovery communication 504. However, the external device thatis providing the proximity communication to this other IMD may haveproperly selected this other IMD and may provide a proximitycommunication that does satisfy the challenge of this other IMD so thata proper communication session may be established between them.

In the event the external device 102 has not adequately responded to thechallenge, the external device 102 will need to re-attempt to discover,select, and establish a session with the intended IMD 104. However,where the external device 102 has selected the IMD 104 from the set offar field responses and responds by providing the proximitycommunication 520 that does satisfy the challenge by the intended IMD104, then the external device 102 and the IMD 104 will both begin thefar field communication session via subsequent far field communications528.

The external device may communicate during the session by using theunique value of the external device 102 of which the IMD 104 has beenmade aware via a far field communication to identify the sender oftransmissions and/or using the unique value of the IMD 104 to identifythe intended recipient of transmissions. Likewise, the IMD 104 maycommunicate during the session by using the unique value of the IMD 104of which the external device 102 is aware to identify the sender oftransmissions and/or using the unique value of the external device 102to identify the intended recipient of transmissions.

As with the example of FIG. 4, the session may be made secure byencrypting the information with an encryption key. This encryption keymay have been generated for the session by the external device 102 andincluded in a far field communication so that the IMD 104 obtains thekey. As one example, the key may be exchanged by using a low power radiofrequency communication to minimize the range. Furthermore, the IMD 104may provide the key for the secure session rather than receiving the keyfrom the external device 102. To the extent the devices have a capablemanner of using more complex proximity communications, the key may beexchanged through proximity communication rather than through far fieldcommunication.

FIG. 6 shows a third example of a procedure to establish a far fieldcommunication session. In this particular example and as furtherdiscussed below, a challenge may be issued by the IMD upon the start ofa far field communication session to provide confirmation that thecorrect IMD has been selected.

Initially, the external device 102 provides a proximity communication602 in the form of a signal. As discussed above, the proximitycommunication 602 may be provided by a third party such as the clinicianacting at the request of the external device 102 such as to pass amagnet nearby the IMD 104 to provide a form of the proximitycommunication 602. In either case, this signal may be simple in terms ofcarrying no data but merely being on or off. Alternatively, this signalof the proximity communication 602 from the external device 102 may bemore sophisticated including the ability to carry data. In either case,the IMD 104 may or may not have the ability to send a return proximitycommunication.

As with FIG. 5, the proximity communication 602 from the external device102 may serve one or more purposes. For instance, the proximitycommunication 602 may serve as a trigger for the IMD 104 to respond tofar field communication. Likewise, the proximity communication 602 mayserve as a wake-up signal to the far field communication abilities ofthe IMD 104.

The external device 102 also sends a far field discovery communication604. This far field discovery communication 604 may occur at some pointshortly after the proximity communication 602, particularly in exampleswhere the proximity communication 602 serves as a wake-up signal to thefar field communication abilities of the IMD 104. The far fielddiscovery communication 604 may occur shortly before or during theproximity communication 602, particularly in examples where the farfield communication abilities of the IMD 104 are already functioningprior to the proximity communication 602.

The far field discovery communication 604 serves as an inquiry to allIMDs within range and triggers the receiving IMDs to provide a responsethat identifies the IMD such as by including a value unique to the IMD104 in the response to the discovery. In one example, the far fielddiscovery communication 604 specifies a condition for responding. Thecondition may be that the IMD responds only if the IMD is receiving thefar field discovery communication 604 within a predefined time relativeto receiving the proximity communication. In one example, the predefinedtime may be zero, such that the IMD must receive the proximitycommunication 602 at the time the far field discovery communication 604is received in order to provide a response.

This condition may be specified by setting a bit value within thediscovery request, where the predefined time is preconfigured within thelogic of the IMD 104. This condition may alternatively be specified in amore complex manner such as by indicating the predefined amount of timewithin the request.

In another example, the criteria for responding are preconfigured withinthe IMD 104. So, in this case, the far field discovery communication 604may omit any conditions, and the external device 102 may rely on theIMDs that receive the far field discovery communication 604 to properlydetermine whether to respond based upon the preconfiguration.

In this example, the IMD 104 detects whether the far field discoverycommunication has arrived within the predefined amount of time relativeto receiving the proximity communication 602 at a query operation 606.For those IMDs where no proximity communication 602 has been received orhas been received such that the far field discovery communication 604 isoutside of the allowed window of time, the far field discoverycommunication 604 is ignored at an operation 608. For the intended IMD104, the proximity communication 602 is received and the far fielddiscovery communication arrives within the predefined time relative tothe proximity communication 602 so that a far field responsecommunication 610 is returned.

The far field response communication 610 may specify the value that isunique to the IMD 104. The external device 102 may then utilize thisunique value to establish a communication session with the IMD 104.However, there is the possibility that multiple IMDs provide a responsein this example as well. These responding devices may include theintended IMD 104 as well as the other nearby IMDs who may have also hada proximity signal from other external devices present at theappropriate time relative to the far field discovery communication 604from the external device 102. In that case, the external device 102 maynot determine which IMD 104 is the correct one from the far fieldresponses alone. The external device 102 may instead rely on anotherchallenge procedure in order to ultimately confirm that the intended IMD104 is the one that the external device 102 is communicating with viafar field communications.

In this example, the challenge procedure may be provided by the externaldevice 102 entering into a communication session with a selected one ofthe responding IMDs. The choice of IMD may be based on time the responsewas received, strength of the response signal, a random selection, andthe like. The external device 102 then attempts to satisfy the challengeand then proceeds with the session if the challenge is satisfied orterminates the current session due to a failed challenge. If a challengeis failed, the external device 102 then starts a session with the nextselected responding IMD to attempt to satisfy that challenge and thisprocess continues until a challenge for a responding IMD is satisfied.As an alternative, the challenge procedure may be provided by theexternal device 102 entering into separate and simultaneouscommunication sessions with all of the responding IMDs. The externaldevice 102 then attempts to satisfy the challenge of each one insequence where sessions with failed challenges terminate and the sessionwith the satisfied challenge proceeds.

When choosing whether to respond to any one of the received responses byestablishing a communication session, the external device 102 may detectwhether each response is timely at a query operation 612 and ignore theresponse at an operation 614 if not. The external device 102 may thenproceed to setup the far field communication session(s) for the chosenresponse or alternatively for each of the responses.

The external device 102 may proceed to associate the unique value of theIMD received in the response to a given far field communication sessionat an association operation 616 and being far field communications 618.The external device 102 may also then execute the appropriate therapyprogram automatically based on the value that is unique to the IMD wherethe external device 102 stores associations of such values to therapyapplications.

The external device 102 may communicate during the session by using theunique value of the external device 102 of which the IMD of the sessionhas been made aware via a far field communication to identify the senderof transmissions and/or using the unique value of the IMD of the sessionto identify the intended recipient of transmissions. Likewise, the IMDof the session may communicate during the session by using the uniquevalue of the IMD of the session of which the external device 102 isaware to identify the sender of transmissions and/or using the uniquevalue of the external device 102 to identify the intended recipient oftransmissions.

As with the example of FIG. 4, each session may be made secure byencrypting the information with an encryption key, where each sessionmay utilize a different key. This encryption key may have been generatedfor the session by the external device 102 and included in a far fieldcommunication so that the IMD of the session obtains the key.Furthermore, the IMD 104 may provide the key for the secure sessionrather than receiving the key from the external device 102.

Upon starting the communication session, the external device 102 of thisparticular example then sends a far field communication 620 thatincludes a challenge request that is addressed with the unique value ofthe IMD of the session. The challenge request triggers the IMD of thesession to return a challenge and to monitor for a challenge responsevia a proximity communication. In some embodiments, the IMD may detectwhether the proximity challenge is timely and if not, then ignoresubsequent far field communications from the external device 102.

When appropriate, the IMD of each of the sessions sends the far fieldcommunication 622 that may include the unique value of the externaldevice 102 and includes the challenge. The challenge may specify thatthe external device 102 provide a proximity communication that includesa challenge response. As discussed above for the example in FIG. 5, thechallenge response may be of various types and may depend upon the typeof proximity communication that is in use. For instance, where theproximity communication is a simple on or off state of a signal, thechallenge may be to provide an on-off sequence, or to be on at only acertain time or for only a certain duration. As another example, wherethe proximity communication is capable of providing data, the challengemay be to repeat a particular data value or sequence.

The external device 102 then sends a proximity communication 624 for thesession or sessions that provides the response to the challenge. Theproximity communication 624 may also be addressed with the unique valueof the IMD of the session. Then the external device 102 attempts tocontinue the communication session with the IMD of the session via anexchange of subsequent far field communications 630.

The IMD of the session detects whether the shared challenge is verifiedby detecting whether the challenge response has been received andmatches the challenge that was issued at a query operation 626. Becausethe IMD 104 is receiving proximity communications from the externaldevice 102, the IMD 104 will receive the proximity communication 624that includes the challenge response regardless of whether the externaldevice 102 is responding to the challenge by the IMD 104 or a challengeby another nearby IMD. In the situation where the IMD 104 has yet toissue the challenge either because the external device 102 has yet toestablish the communication session with the IMD 104 or because it isnot yet the turn of the IMD 104 to receive a challenge request, then theIMD 104 may simply ignore the proximity communication 624.

In that case, the proximity communication that includes the challengeresponse is a result of the external device 102 responding to achallenge by another nearby IMD. This other nearby IMD that has beenincorrectly selected by the external device 102 will not receive theproximity communication 624 that includes the challenge response becausethis other nearby IMD is not within range of the proximity communication624. Thus, this other nearby IMD will detect that a matching responsehas not been received at a query operation 626. As a result, the othernearby IMD also ignores all subsequent communication at an operation 628until the discovery process of FIG. 6 re-starts with another proximitycommunication 602 and far field discovery communication 604.

In the event the external device 102 has not adequately responded to thechallenge, the external device 102 will need to re-attempt to discover,select, and establish a session with the intended IMD 104. However,where the external device 102 has selected the IMD 104 from the set offar field responses and responds by providing the proximitycommunication 624 that does satisfy the challenge by the intended IMD104 at the query operation 626, then the external device 102 and the IMD104 will both continue the far field communication session viasubsequent far field communications 630. The external device 102 maythen cease attempting to satisfy any remaining challenges of otherresponding IMDs, and those IMDs ignore subsequent communications untilthe discovery process of FIG. 6 re-starts.

FIG. 7 shows a fourth example of a procedure to establish a far fieldcommunication session. In this particular example and as furtherdiscussed below, a challenge may be issued by the IMD 104 at the onsetof the far field communication session to provide confirmation that thecorrect IMD has been selected. Additionally or alternatively, the IMD104 may issue the challenge at one or more subsequent times during thecommunication session which allows the IMD 104 to periodically confirmthat far field communications are with the intended external device 102.

Initially, the external device 102 provides a proximity communication702 in the form of a signal. As discussed above, the proximitycommunication 702 may be provided by a third party such as the clinicianacting at the request of the external device 102 such as to pass amagnet nearby the IMD 104 to provide a form of the proximitycommunication 702. In either case, this signal may be simple in terms ofcarrying no data but merely being on or off. Alternatively, this signalof the proximity communication 702 from the external device 102 may bemore sophisticated including the ability to carry data. In either case,the IMD 104 may or may not have the ability to send a return proximitycommunication.

As with FIG. 5, the proximity communication 702 from the external device102 may serve one or more purposes. For instance, the proximitycommunication 702 may serve as a trigger for the IMD 104 to respond tofar field communication. Likewise, the proximity communication 702 mayserve as a wake-up signal to the far field communication abilities ofthe IMD 104.

The external device 102 also sends a far field discovery communication704. This far field discovery communication 704 may occur at some pointshortly after the proximity communication 702, particularly in exampleswhere the proximity communication 702 serves as a wake-up signal to thefar field communication abilities of the IMD 104. The far fielddiscovery communication 704 may occur shortly before or during theproximity communication 702, particularly in examples where the farfield communication abilities of the IMD 104 are already functioningprior to the proximity communication 702.

The far field discovery communication 704 serves as an inquiry to allIMDs within range and triggers the receiving IMDs to provide a responsethat identifies the IMD such as by including a value unique to the IMD104 in the response to the discovery. In one example, the far fielddiscovery communication 704 specifies a condition for responding. Thecondition may be that the IMD responds only if the IMD is receiving thefar field discovery communication 704 within a predefined time relativeto receiving the proximity communication. In one example, the predefinedtime may be zero, such that the IMD must receive the proximitycommunication 702 at the time the far field discovery communication 704is received in order to provide a response.

This condition may be specified by setting a bit value within thediscovery request, where the predefined time is preconfigured within thelogic of the IMD 104. This condition may alternatively be specified in amore complex manner such as by indicating the predefined amount of timewithin the request.

In another example, the criteria for responding are preconfigured withinthe IMD 104. So, in this case, the far field discovery communication 704may omit any conditions, and the external device 102 may rely on theIMDs that receive the far field discovery communication 704 to properlydetermine whether to respond based upon the preconfiguration.

In this example, the IMD 104 detects whether the far field discoverycommunication has arrived within the predefined amount of time relativeto receiving the proximity communication 702 at a query operation 706.For those IMDs where no proximity communication 702 has been received orhas been received such that the far field discovery communication 704 isoutside of the allowed window of time, the far field discoverycommunication 704 is ignored at an operation 708. For the intended IMD104, the proximity communication 702 is received and the far fielddiscovery communication arrives within the predefined time relative tothe proximity communication 702 so that a far field responsecommunication 710 is returned.

The far field response communication 710 may specify the value that isunique to the IMD 104. The external device 102 may then utilize thisunique value to establish a communication session with the IMD 104.However, there is the possibility that multiple IMDs provide a responsein this example as well. These responding devices may include theintended IMD 104 as well as the other nearby IMDs who may have also hada proximity signal from other external devices present at theappropriate time relative to the far field discovery communication 704from the external device 102. In that case, the external device 102 maynot determine which IMD 104 is the correct one from the far fieldresponses alone. The external device 102 may instead rely on anotherchallenge procedure in order to ultimately confirm that the intended IMD104 is the one that the external device 102 is communicating with viafar field communications.

In this example, the challenge procedure may be provided by the externaldevice 102 entering into a communication session with a selected one ofthe responding IMDs. The choice of IMD may be based on time the responsewas received, strength of the response signal, a random selection, andthe like. The external device 102 then attempts to satisfy the challengeand then proceeds with the session if the challenge is satisfied orterminates the current session due to a failed challenge. If a challengeis failed, the external device 102 then starts a session with the nextselected responding IMD to attempt to satisfy that challenge and thisprocess continues until a challenge for a responding IMD is satisfied.As an alternative, the challenge procedure may be provided by theexternal device 102 entering into separate and simultaneouscommunication sessions with all of the responding IMDs. The externaldevice 102 then attempts to satisfy the challenge of each one insequence where sessions with failed challenges terminate and the sessionwith the satisfied challenge proceeds.

When choosing whether to respond to any one of the received responses byestablishing a communication session, the external device 102 may detectwhether each response is timely at a query operation 712 and ignore theresponse at an operation 714 if not. The external device 102 may thenproceed to setup the far field communication session(s) for the chosenresponse or alternatively for each of the responses.

The external device 102 may proceed to associate the unique value of theIMD received in the response to a given far field communication sessionat an association operation 716 and begin sending far fieldcommunications 718. The external device 102 may also then execute theappropriate therapy program automatically based on the value that isunique to the IMD where the external device 102 stores associations ofsuch values to therapy applications.

The external device 102 may communicate during the session by using theunique value of the external device 102 of which the IMD of the sessionhas been made aware via a far field communication to identify the senderof transmissions and/or using the unique value of the IMD of the sessionto identify the intended recipient of transmissions. Likewise, the IMDof the session may communicate during the session by using the uniquevalue of the IMD of the session of which the external device 102 isaware to identify the sender of transmissions and/or using the uniquevalue of the external device 102 to identify the intended recipient oftransmissions.

As with the example of FIG. 4, each session may be made secure byencrypting the information with an encryption key, where each sessionmay utilize a different key. This encryption key may have been generatedfor the session by the external device 102 and included in a far fieldcommunication so that the IMD of the session obtains the key.Furthermore, the IMD of the session may provide the key for the securesession rather than receiving the key from the external device 102.

Upon starting the communication session(s), the IMD of a session in thisparticular example begins detecting whether it is time to challenge theexternal device 102 at a query operation 720. For instance, the IMD of asession may be configured to challenge the IMD immediately upon thecommunication session being established. In this case, the IMD of asession may challenge the external device 102 to provide confirmation atthe onset of the communication session without the external device 102first having to request the challenge. Furthermore, the IMD of a sessionadditionally or alternatively determines that such a challenge isnecessary at some later time during the session so that confirmationthroughout the session may occur. It will be appreciated that in someexamples, the external device 102 may request one or more challenges, asin FIG. 6, while the IMD 104 may respond to those and may also generateone or more challenges to the external device 102 without receiving arequest as in FIG. 7.

In the example of FIG. 7, the IMD of the session sends the far fieldcommunication 722 that includes the challenge. The challenge may specifythat the external device 102 provide a proximity communication thatincludes a challenge response. As discussed above for the example inFIG. 5, the challenge response may be of various types and may dependupon the type of proximity communication that is in use. For instance,where the proximity communication is a simple on or off state of asignal, the challenge may be to provide an on-off sequence, or to be onat only a certain time or for only a certain duration. As anotherexample, where the proximity communication is capable of providing data,the challenge may be to repeat a particular data value or sequence.

The external device 102 then sends a proximity communication 724 for thesession that provides the response to the challenge. Then the externaldevice 102 attempts to continue the communication session with the IMDof the session via an exchange of subsequent far field communications730.

The IMD of the session detects whether the shared challenge is verifiedby detecting whether the challenge response has been received andmatches the challenge that was issued at a query operation 726. Becausethe intended IMD 104 is receiving proximity communications from theexternal device 102, the intended IMD 104 will receive the proximitycommunication 724 that includes the challenge response regardless ofwhether the external device 102 is responding to the challenge by theIMD 104 or a challenge by another nearby IMD. In the situation where theIMD 104 has yet to issue the challenge because the external device 102has yet to establish the communication session with the IMD 104, thenthe IMD 104 may simply ignore the proximity communication 724.

In that case, the proximity communication that includes the challengeresponse is a result of the external device 102 responding to achallenge by another nearby IMD. This other nearby IMD that has beenincorrectly selected by the external device 102 will not receive theproximity communication 724 that includes the challenge response becausethis other nearby IMD is not within range of the proximity communication724. Thus, this other nearby IMD will detect that a matching responsehas not been received at a query operation 726. As a result, the othernearby IMD also ignores all subsequent communication and terminates thesession at an operation 728 until the discovery process of FIG. 7re-starts with another proximity communication 702 and far fielddiscovery communication 704.

In the event the external device 102 has not adequately responded to thechallenge, the external device 102 will need to re-attempt to discover,select, and establish a session with the intended IMD 104. However,where the external device 102 has selected the IMD 104 from the set offar field responses and responds by providing the proximitycommunication 724 that does satisfy the challenge by the intended IMD104 at the query operation 726, then the external device 102 and the IMD104 will both continue the far field communication session viasubsequent far field communications 730 until the time for the nextchallenge by the IMD 104 arrives. Upon satisfying the first challenge bythe IMD 104, the external device 102 may then cease attempting tosatisfy any remaining challenges of other responding IMDs, and thoseIMDs ignore subsequent communications until the discovery process ofFIG. 7 re-starts.

FIG. 8 shows a fifth example of a procedure to establish a far fieldcommunication session. In this particular example, the external device102 relies upon the uniqueness of an encryption key for the secure farfield session with the IMD 104 together with the security of theproximity communication as a manner of confirming that the intended IMD104 has been selected for the far field communication.

Initially, the external device 102 provides a proximity communication802 in the form of a signal. As discussed above, the proximitycommunication 802 may be provided by a third party such as the clinicianacting at the request of the external device 102 such as to pass amagnet nearby the IMD 104 to provide a form of the proximitycommunication 802. In either case, this signal may be simple in terms ofcarrying no data but merely being on or off. Alternatively, this signalof the proximity communication 802 from the external device 102 may bemore sophisticated including the ability to carry data. In either case,the IMD 104 may or may not have the ability to send a return proximitycommunication.

As with FIG. 5, the proximity communication 802 from the external device102 may serve one or more purposes. For instance, the proximitycommunication 802 may serve as a trigger for the IMD 104 to respond tofar field communication. Likewise, the proximity communication 802 mayserve as a wake-up signal to the far field communication abilities ofthe IMD 104. Furthermore, in some cases, the proximity communication 802may provide the encryption key to the IMD 104.

The external device 102 also sends a far field discovery communication804. This far field discovery communication 804 may occur at some pointshortly after the proximity communication 802, particularly in exampleswhere the proximity communication 802 serves as a wake-up signal to thefar field communication abilities of the IMD 104. The far fielddiscovery communication 804 may occur shortly before or during theproximity communication 802, particularly in examples where the farfield communication abilities of the IMD 104 are already functioningprior to the proximity communication 802.

The far field discovery communication 804 serves as an inquiry to allIMDs within range and triggers the receiving IMDs to provide a responsethat identifies the IMD such as by including a value unique to the IMD104 in the response to the discovery. In one example, the far fielddiscovery communication 804 specifies a condition for responding. Thecondition may be that the IMD responds only if the IMD is receiving thefar field discovery communication 804 within a predefined time relativeto receiving the proximity communication. In one example, the predefinedtime may be zero, such that the IMD must receive the proximitycommunication 802 at the time the far field discovery communication 804is received in order to provide a response.

This condition may be specified by setting a bit value within thediscovery request, where the predefined time is preconfigured within thelogic of the IMD 104. This condition may alternatively be specified in amore complex manner such as by indicating the predefined amount of timewithin the request.

In another example, the criteria for responding are preconfigured withinthe IMD 104. So, in this case, the far field discovery communication 804may omit any conditions, and the external device 102 may rely on theIMDs that receive the far field discovery communication 804 to properlydetermine whether to respond based upon the preconfiguration.

In this example, the IMD 104 detects whether the far field discoverycommunication has arrived within the predefined amount of time relativeto receiving the proximity communication 802 at a query operation 806.For those IMDs where no proximity communication 802 has been received orhas been received such that the far field discovery communication 804 isoutside of the allowed window of time, the far field discoverycommunication 804 is ignored at an operation 808. For the intended IMD104, the proximity communication 802 is received and the far fielddiscovery communication arrives within the predefined time relative tothe proximity communication 802 so that a far field responsecommunication 810 is returned.

The far field response communication 810 may specify the value that isunique to the IMD 104. The external device 102 may then utilize thisunique value to establish a communication session with the IMD 104.However, there is the possibility that multiple IMDs provide a responsein this example as well. These responding devices may include theintended IMD 104 as well as the other nearby IMDs who may have also hada proximity signal from other external devices present at theappropriate time relative to the far field discovery communication 804from the external device 102. In that case, the external device 102 maynot determine which IMD 104 is the correct one from the far fieldresponses alone. The external device 102 may instead rely on an exchangeof a unique encryption key via a proximity communication.

In this example, the key encryption procedure may be provided by theexternal device 102 entering into a communication session with aselected one of the responding IMDs. The choice of IMD may be based ontime the response was received, strength of the response signal, arandom selection, and the like. The external device 102 then attempts toexchange the encryption key via a proximity communication and then beginfar field communications using the key. If far field communicationsfail, the external device 102 then starts a session with the nextselected responding IMD to attempt to exchange the encryption key andthen begin far field communications. As an alternative, the exchange ofthe key may be provided followed by the external device 102 enteringinto separate and simultaneous far field communication sessions with allof the responding IMDs. The external device 102 then attempts tocommunicate using data encrypted by the encryption key via the far fieldcommunication session with each one where sessions with failed far fieldcommunication attempts terminate and the session with the successful farfield communication proceeds.

When choosing whether to respond to any one of the received responses byestablishing a far field communication session, the external device 102may detect whether each response is timely at a query operation 812 andignore the response at an operation 814 if not. The external device 102may then proceed to setup the secure far field communication session(s)for the chosen response or alternatively for each of the responses.

The external device 102 may proceed to associate the unique value of theIMD received in the response to a given far field communication sessionat an association operation 816 and then send a proximity communication818 that includes the encryption key. The external device 102 may alsothen execute the appropriate therapy program automatically based on thevalue that is unique to the IMD 104 where the external device 102 storesassociations of such values to therapy applications.

The external device 102 may then begin sending secure far fieldcommunications 818. The external device 102 may communicate during thesession by using the unique value of the external device 102 of whichthe IMD of the session has been made aware via a far field communicationto identify the sender of transmissions and/or using the unique value ofthe IMD of the session to identify the intended recipient oftransmissions. Likewise, the IMD of the session may communicate duringthe session by using the unique value of the IMD of the session of whichthe external device 102 is aware to identify the sender of transmissionsand/or using the unique value of the external device 102 to identify theintended recipient of transmissions.

Upon starting the communication session(s), the IMD of a session in thisparticular example begins detecting whether any incoming communicationscan be decrypted. Because the intended IMD 104 is receiving proximitycommunications from the external device 102, the intended IMD 104 willreceive the proximity communication 818 that includes the encryption keyregardless of whether the external device 102 is attempting tocommunicate with the IMD 104 or with another nearby IMD.

In one example where the external device 102 is proceeding with onesecure far field session at a time, the external device 102 may providethe proximity communication 818 before each attempt at a secure farfield communication session. In that case, if the IMD 104 has yet toreceive a secure far field communication from the external device 102because it is not yet the turn of the IMD 104, then the IMD 104 maysimply ignore the proximity communication 818 after a timeout period. Inanother example where the external device 102 is proceeding with onesecure far field session at a time, the external device 102 may providethe proximity communication 818 a single time and then rely on theintended IMD 104 to retain the encryption key until it is the turn ofthe intended IMD 104 to begin secure far field communications.Furthermore, in that case the key exchange may be provided at theinitial proximity communication 802 as opposed to providing theproximity communication 818.

A secure far field communication attempt being sent by the externaldevice 102 may be addressed to another nearby IMD. This other nearby IMDthat has been incorrectly selected by the external device 102 has notreceived the proximity communication 818 that includes the encryptionkey because this other nearby IMD is not within range of the proximitycommunication 818. Thus, this other nearby IMD will not be able todecrypt the secure far field communication attempt. As a result, theother nearby IMD will not respond which terminates the session with thatother IMD. This other IMD may then wait for the discovery process ofFIG. 8 re-starts with another proximity communication 802 and far fielddiscovery communication 804.

In the event the external device 102 has not successfully establishedsecure far field communications with the IMD 104, the external device102 will need to re-attempt to discover, select, and establish a sessionwith the intended IMD 104. However, where the external device 102 hasselected the IMD 104 from the set of far field responses and responds byproviding the proximity communication 818, then the external device 102and the IMD 104 will both begin exchanging secure far fieldcommunications 820.

FIG. 9 shows a sixth example of a procedure to establish a far fieldcommunication session. In this particular example, the external device102 relies upon a strength of far field signal between the externaldevice 102 and the responding IMDs as a manner of confirming that theintended IMD 104 has been selected for the far field communication. Thismay be a valid manner of confirmation considering that the odds of anearby IMD receiving a proximity communication at the proper time inorder to trigger the response to the discovery message coupled with astrength of signal for that nearby IMD being stronger than the strengthof the intended IMD 104 are relatively low.

The signal strength of interest may vary from one example to the next.For instance, the signal strength may be from the perspective of the IMDfor a far field communication sent by the external device 102 such as adiscovery message. That signal strength may be reported by the IMD in aresponse to the discovery message. The signal strength may be from theperspective of the external device 102 for a far field communicationsent by the IMD such as the response to the discovery message. Thesignal strength may be based on a combination of these values and may bebased on other far field communications between the external device 102and the IMD as well.

Initially, the external device 102 provides a proximity communication902 in the form of a signal. As discussed above, the proximitycommunication 902 may be provided by a third party such as the clinicianacting at the request of the external device 102 such as to pass amagnet nearby the IMD 104 to provide a form of the proximitycommunication 902. In either case, this signal may be simple in terms ofcarrying no data but merely being on or off. Alternatively, this signalof the proximity communication 902 from the external device 102 may bemore sophisticated including the ability to carry data. In either case,the IMD 104 may or may not have the ability to send a return proximitycommunication.

As with FIG. 5, the proximity communication 902 from the external device102 may serve one or more purposes. For instance, the proximitycommunication 902 may serve as a trigger for the IMD 104 to respond tofar field communication. Likewise, the proximity communication 902 mayserve as a wake-up signal to the far field communication abilities ofthe IMD 104.

The external device 102 also sends a far field discovery communication904. This far field discovery communication 904 may occur at some pointshortly after the proximity communication 902, particularly in exampleswhere the proximity communication 902 serves as a wake-up signal to thefar field communication abilities of the IMD 104. The far fielddiscovery communication 904 may occur shortly before or during theproximity communication 902, particularly in examples where the farfield communication abilities of the IMD 104 are already functioningprior to the proximity communication 902.

The far field discovery communication 904 serves as an inquiry to allIMDs within range and triggers the receiving IMDs to provide a responsethat identifies the IMD such as by including a value unique to the IMD104 in the response to the discovery. In one example, the far fielddiscovery communication 904 specifies a condition for responding. Thecondition may be that the IMD responds only if the IMD is receiving thefar field discovery communication 904 within a predefined time relativeto receiving the proximity communication. In one example, the predefinedtime may be zero, such that the IMD must receive the proximitycommunication 902 at the time the far field discovery communication 904is received in order to provide a response.

This condition may be specified by setting a bit value within thediscovery request, where the predefined time is preconfigured within thelogic of the IMD 104. This condition may alternatively be specified in amore complex manner such as by indicating the predefined amount of timewithin the request.

In another example, the criteria for responding are preconfigured withinthe IMD 104. So, in this case, the far field discovery communication 904may omit any conditions, and the external device 102 may rely on theIMDs that receive the far field discovery communication 904 to properlydetermine whether to respond based upon the preconfiguration.

In this example, the IMD 104 detects whether the far field discoverycommunication has arrived within the predefined amount of time relativeto receiving the proximity communication 902 at a query operation 906.For those IMDs where no proximity communication 902 has been received orhas been received such that the far field discovery communication 904 isoutside of the allowed window of time, the far field discoverycommunication 904 is ignored at an operation 908. For the intended IMD104, the proximity communication 902 is received and the far fielddiscovery communication arrives within the predefined time relative tothe proximity communication 902 so that a far field responsecommunication 910 is returned.

The far field response communication 910 may specify the value that isunique to the IMD 104. The external device 102 may then utilize thisunique value to establish a communication session with the IMD 104. Thefar field response communication 910 may also specify a signal strengthsuch as that as detected by the responding IMD for the far fielddiscovery communication 904. Additionally or alternatively, the externaldevice 102 may collect the signal strength of the far field responsecommunication 910. There is the possibility that multiple IMDs provide aresponse in this example as well, and the external device 102 collectssignal strength information for each response. These responding devicesmay include the intended IMD 104 as well as the other nearby IMDs whomay have also had a proximity signal from other external devices presentat the appropriate time relative to the far field discoverycommunication 904 from the external device 102. In that case, theexternal device 102 may not determine which IMD 104 is the correct onefrom the far field responses alone. The external device 102 may insteadrely on the collected signal strength related to the responding IMDs.

When choosing whether to respond to any one of the received responses byestablishing a far field communication session, the external device 102may detect whether each response is timely at a query operation 912 andignore the response at an operation 914 if not. As stated above, theexternal device 102 collects the signal strength information for each ofthe responding IMDs. The external device 102 may continue to receive andcollect the signal strength information until determining at a queryoperation 916 that a response period has ended. The external device 102may then determine for each responding IMD whether that IMD isassociated with the strongest signal at a query operation 918. Theseoperations are iterated for to account for each IMD 104.

If a responding IMD is not associated with the strongest signal, thenthe external device ignores the response at the operation 914. However,for the responding IMD that is associated with the strongest signal, theexternal device 102 proceeds to associate the unique value of thatresponding IMD that was received in the far field response communication910 to the far field communication session at an association operation920. The external device 102 may also then execute the appropriatetherapy program automatically based on the value that is unique to theIMD 104 where the external device 102 stores associations of such valuesto therapy applications.

The external device 102 may then communicate during the session by usingthe unique value of the external device 102 of which the IMD 104 hasbeen made aware via a far field communication to identify the sender oftransmissions and/or using the unique value of the IMD 104 to identifythe intended recipient of transmissions. Likewise, the IMD 104 maycommunicate during the session by using the unique value of the IMD 104of which the external device 102 is aware to identify the sender oftransmissions and/or using the unique value of the external device 102to identify the intended recipient of transmissions.

To further ensure that the IMD that has been selected based on signalstrength is the intended IMD, other techniques may then be performed.For instance, a challenge procedure initiated by the external device 102as in FIG. 6 or initiated by the IMD 104 as in FIG. 7 may be conducted.As another example, the encryption key may be exchanged via proximitycommunication as in FIG. 8.

Regardless of whether a procedure similar to that of FIG. 8 is used forfurther confirmation, the session may be made secure by encrypting theinformation with an encryption key. This encryption key may have beengenerated for the session by the external device 102 and included in afar field communication so that the IMD 104 obtains the key. As oneexample, the key may be exchanged by using a low power radio frequencycommunication to minimize the range. Furthermore, the IMD 104 mayprovide the key for the secure session rather than receiving the keyfrom the external device 102. To the extent the devices have a capablemanner of using more complex proximity communications, the key may beexchanged through proximity communication rather than through far fieldcommunication as discussed above for FIG. 8.

With regard to FIGS. 4-9, it will be appreciated that the roles of theexternal device 102 and IMD 104 may be reversed. As one example, inrelation to FIG. 5, the external device may issue the challenge to theIMD, and the IMD 104 may have the ability to send proximitycommunications while the external device 102 receives them. As anotherexample, in relation to FIG. 6, the IMD 104 may request that theexternal device 102 issue a challenge that the IMD 104 then responds tovia a proximity communication. As yet another example, in relation toFIG. 7, the external device 102 may periodically challenge the IMD 104which responds via a proximity communication.

While embodiments have been particularly shown and described, it will beunderstood by those skilled in the art that various other changes in theform and details may be made therein without departing from the spiritand scope of the invention.

1-12. (canceled)
 13. A method of establishing communication between anexternal device and an implantable medical device, comprising:transmitting a proximity communication to the implantable medicaldevice, the proximity communication comprising a value that is unique tothe external device; transmitting a far field discovery communication;and after transmitting the far field discovery communication, receivinga far field response communication, the far field response communicationcomprising a value that is unique to the implantable medical device anda second value; comparing the second value to the value that is uniqueto the external device; if the second value is the same as the valuethat is unique to the external device, then exchanging information withthe implantable device using far field communication by receiving theinformation together with the value that is unique to the implantablemedical device.
 14. The method of claim 13, wherein the proximitycommunication to the implantable medical device further includes anencryption key.
 15. The method of claim 14, wherein exchanginginformation with the implantable medical device using far fieldcommunication comprises decrypting the information with the encryptionkey.
 16. The method of claim 13, wherein exchanging information with theimplantable medical device further comprises using far fieldcommunication by transmitting the information in conjunction with thevalue that is unique to the external device. 17-20. (canceled)
 21. Asystem for establishing communication, comprising: an external deviceand an implantable medical device, wherein the external device isconfigured to: transmit a proximity communication to the implantablemedical device, the proximity communication comprising a value that isunique to the external device; transmit a far field discoverycommunication; after transmit the far field discovery communication,receiving a far field response communication, the far field responsecommunication comprising a value that is unique to the implantablemedical device and a second value; compare the second value to the valuethat is unique to the external device; if the second value is the sameas the value that is unique to the external device, then exchangeinformation with the implantable device using far field communication byreceiving the information together with the value that is unique to theimplantable medical device.
 22. The system of claim 21, wherein theproximity communication to the implantable medical device furtherincludes an encryption key.
 23. The system of claim 22, wherein theexternal device exchanges information with the implantable medicaldevice using far field communication by decrypting the information withthe encryption key.
 24. The system of claim 21, wherein the externaldevice exchanges information with the implantable medical device usingfar field communication by transmitting the information in conjunctionwith the value that is unique to the external device.
 21. A system forestablishing communication, comprising: an external device and animplantable medical device, wherein the external device is configuredto: transmit a proximity communication to the implantable medicaldevice, the proximity communication comprising a value that is unique tothe external device; transmit a far field discovery communication; aftertransmit the far field discovery communication, receiving a far fieldresponse communication, the far field response communication comprisinga value that is unique to the implantable medical device and a secondvalue; compare the second value to the value that is unique to theexternal device; if the second value is the same as the value that isunique to the external device, then exchange information with theimplantable device using far field communication by receiving theinformation together with the value that is unique to the implantablemedical device.
 22. The system of claim 21, wherein the proximitycommunication to the implantable medical device further includes anencryption key.
 23. The system of claim 22, wherein the external deviceexchanges information with the implantable medical device using farfield communication by decrypting the information with the encryptionkey.
 24. The system of claim 21, wherein the external device exchangesinformation with the implantable medical device using far fieldcommunication by transmitting the information in conjunction with thevalue that is unique to the external device.